Tenacity As Post-Emergent to Kill Nimblewill - August 2022
Last week, I shared here on my lawn diary a little breakthrough. For the past 18-or-so months, I've been watching a grassy weed creep along and begin to migrate from my far backyard to closer to our patio. And, after reading about various grassy weeds, I came to the (initial) conclusion that I was dealing with Poa Annua - or an annual Bluegrass. It was showing some of the signs like being lime green. But, after observing the lawn this Spring, I noticed that the parts affected green'd up later and seemed to handle the Summer better than the balance of my Bluegrass. I was planning on doing a complete renovation in the back by killing EVERYTHING off and starting from scratch with a new layer of seed this Fall.
As I prepared for that, I went in to see if I could learn more about what was back there and how much I *really* needed to kill off vs. just overseed.
When I went in and pulled a mature stalk of grass, I discovered it had this sort of horizontal branching structure. When I went looking around on the Web for more details, I figured out I was dealing with a warm-season bent grass called Nimblewill. In researching how to deal with Nimblewill in my cool-season lawn, I discovered that there was a chemical treatment that was selective-enough to kill the Nimblewill while leaving my mix of Kentucky Blue Grass, Tall Fescue and what I think is Perennial Ryegrass in tact: something called Tenacity. I went online and picked up a small - but VERY expensive - bottle of Tenacity. Here, below, is what the bottle looks like:
In researching Tenacity, I learned that it can be applied both as a pre-emergent AND a post-emergent. And, for Nimblewill, the recommendation is for post-emergent spraying when it is actively growing. And when is that for Zone 5b? That's right now - August.
When applied as a post-emergent, the recommendation is to also include a non-ionic surfactant that helps the herbicide 'cling' to the blades of the lawn and weeds. I posted about the surfactant that I used here last week.
The small concentrate of Tenacity comes with a measuring syringe to ensure you get the right dosage mixed in your tank. I chose to mix two gallons of the solution up and applied it across the back. The hallmark of Tenacity is that it will turn the grassy weeds WHITE. I found this timelapse video on YouTube that shows the progression of how the weeds go white over time and you can see around days seven, eight and nine a big change has happened.
I sprayed 3 gallons or so of the stuff all over my Nimblewill and now we wait. Hoping for A LOT of white spots in the coming days.